Silver notes that the cities with the latest arrival times tend to be those that employ a lot of young professionals, college towns and cities whose economies rely on gambling and tourism. A quarter of workers in Atlantic City do not start their day until 11:26 a.m., according to census data. Those in Ithaca, N.Y., where Cornell University is located, start work at around 8:19 a.m.

So what is it about some jobs that allow its workers to clock in later?

"The occupation industrial mix makes a big difference because of how workers integrate with the global economy," said Dr. Liana Sayer, a sociology professor at the University of Maryland and an expert on time use.

In other words, a later start means more of your day overlaps with different time zones, Sayer said. This could be a priority for professionals in cities like New York and San Francisco whose work is more linked to the global economy. Their start times stand in contrast to those who work in farming and agriculture and require daylight hours to generate income. Bakersfield, one of California's most agriculturally rich areas, boasts a 7:17 a.m. median start time to its work day, according to Silver's census data.

Professionals in dense cities might also be influenced by colleagues who hold the same work hours. Another explanation may be that professionals in these areas have longer commute times and therefore end up at work later, said Sayer.

Military towns like Killeen, Texas and Jacksonville, N.C., are home to some of the earliest risers. Hinesville, Ga, workers have the earliest median start time of 7:01 a.m.

The numbers in Silver's report refer to the location of the work and not the residence of the workers. The figures also do not include those who work from home. He used the median start time for each city, which means half of its workers start earlier and the other half starts later.